6-diethylamino-1, 2-dihydroquinolines



United States Patent fi-DIEIHYLAMINO-LZ-DIHYDROQUINOLINES David J.Beaver, Richmond Heights, Mo., Paul lvI. Downey, Gainesville, Fla., andJames 0. Harris, St. Albans, W. Va., assignors to Monsanto ChemicalCompany, St. Louis, Mo., a corporation of Delaware No Drawing.Application August 4, 1953, Serial No. 372,399

6 Claims. (Cl. 260-28S) The present invention relates to new and usefulcompositions of matter. More particularly it relates to 6- diethylaminosubstituted 1,2-dihydroquinolines and to methods for their preparation.

The new class of compounds may be represented by the general formula Non n on g \III/ CHa where R represents hydrogen or an alkyl substituent,as for example methyl, ethyl, propyl, isopropyl, and butyl radicals. Rrepresents a short chain alkyl radical such as methyl, ethyl, propyl orbutyl.

The new compounds possess valuable properties which render them suitablefor a number of uses, outstanding of which is an adjuvant for rubbercompounding. One of the major problems of the rubber industry isprotection of natural and synthetic rubber goods against exposurecracking, that is degradation due to ozone while the rubber article isunder either static or dynamic stress. The problem is a ditficult oneand is aggravated by the fact that in general chemical antioxidants orage retarders have little or no value in protecting againstdeterioration by ozone. The new compounds are efficient anti-exposurecracking agents for sulfur vulcanizable elastomers.

The following examples of the invention illustrate the preparation ofthe new compounds in detail:

EXAMPLE 1 Into a suitable reactor fitted with a feed line for passing inacetone and a trap for collecting by-product water of condensation,there was charged 49.2 grams of N,N- diethyl-p-phenylenediamine and 3.5grams of toluenesultonic acid. The mixture was heated to 135 C. andacetone passed in at the rate of approximately 2.5 moles per hour permole of amine charged until 13.6 ml. of water were collected. Thevolatile constituents from the reactor were fed to the center of afractionating column where the unreacted acetone was stripped out andfed back to the reactor, the by-product water being collected in areboiler at the bottom of the column maintained at 100 C. The productwas then heated under reduced pressure for about 30 minutes to removeany readily volatile constituents remaining. The crude product Weighed78.6 grams. The product was further purified by fractional distillation.The 6diethylamino-1,2-dihydro-2,2,4- trimethylquinoline had a boilingpoint of 115-120" C./ 1 mm., n =1.57l8.

EXAMPLE 2 Into a reactor fitted with a reflux condenser there wascharged 55.4 grams of 6-diethylamino-1,2-dihydro-2,2,4-trimethylquinoline, 32.1 grams of methyl iodide, 26.6 grams of sodiumcarbonate and 280 ml. of water. The

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mixture was heated at refluxing temperature for about 12 hours, theorganic layer separated and distilled under reduced pressure. The6-diethylamino-1,2-dihydro-1,2,2,4- tetramethylquinoline was separatedfrom the crude reaction mixture by distillation at reduced pressure.

As illustrated, the preparation of the new compounds is affected bycondensing N,N-diethyl-p-phenylenediamine with a methyl ketone in amolar ratio of at least 1:2 in the presence of a suitable catalyst, suchas toluenesulfonic acid, benzenesulfonic acid, sulfuric acid, iodine orbromine. Examples of suitable methyl ketones are acetone, methyl ethylketone, methyl isopropyl ketone, and methyl butyl ketone. Forintroducing an alkyl substituent in the l-position of a6-diethylamino-l,2-dihydro-2,2,4-trialkylquinoline the iodides are themost satisfactory due to their greater reactivity. However, the bromidesare adequate in-rnany instances and in some cases chlorides condensesatisfactorily. The reactivity of chlorides is enhanced sharply by usingthem in conjunction with a small amount of potassium iodide.

Further examples of the invention are: 6-diethylamino- 1,Z-dihydro-2,diethyl-2-methylquinoline, 6-diethylamino-1,2-dihydro-1-methyl-2,4-diethyl 2 methylquinoline, 6-diethylamino-1,2-dihydro-l-ethyl-2,2,4-trimethylquinoline,

' 6diethylamino 1,2 dihydro 1 butyl-2,2,4-trimethylquinoline.

As illustrative of the anti-exposure cracking properties in vulcanizedsulfur vulcanizable synthetic rubber-like materials, stocks wereprepared from butadiene-l,3-styrene copolymer compositions utilizing thefollowing ingredients:

The stocks so compounded were cured in a press for 30 minutes at 144 C.The vulcanizates were evaluated under dynamic conditions in anatmosphere containing a definite concentration of ozone. Samples of thestocks were cured in the form of a belt /2 Wide, A thick and 5% diameterand mounted on 1" diameter shafts. The ozone concentration wasmaintained at 2030 parts per hundred million throughout the test and theshafts were rotated at R. P. M. In this manner a momentary elongationthrough a range of 020% was provided at any portion of the test specimenpassing over the shaft. (The apparatus and procedure employed aredescribed in a paper of Creed et al. entitled An Apparatus for theEvaluation of Ozone Protective Agents for Elastorners under DynamicConditions given at the Cincinnati, Ohio, Meeting of the Rubber Divisionof the American Chemical Society May 1, 1952). The experimental testspecimens were compared visually at various intervals noting the extentof cracking. A stock which is severely cracked has no service liferemaining in terms of the useful life of a rubber article and where thecracking is designated as extremely severe the degradation is wellbeyond even this point. The results of the tests are set forth below:

3 It is intended to cover all changes and modifications of the examplesof the invention herein chosen for purposes of disclosure which do notconstitute departures from the spirit and scope of the invention.

What is claimed is: 1. The compounds of the general formula where R isselected from the group consisting of hydrogen and alkyl radicalscontaining one to four carbon atoms and R represents an alkyl radical-ofone to four carbon atoms.

2. The compounds of the general formula 4 where R represents an alkylradical of one to four carbon atoms.

3. The compounds of the general formula References Cited in the file ofthis patent UNITED STATES PATENTS Ter Horst May 26, 1931 Paul Aug. 7,1945

1. THE COMPOUNDS OF THE GENERAL FORMULA